Migration to new multiplatorm plugin (#947)

Migration to a new multiplatform plugin
  
  * kotlinx-coroutines-core-[common|js|native] are merged into one core module with multiple source sets
  * Folder structure and readme are restructured
  * Publication process is patched to preserve backward compatibility with artifact names
diff --git a/docs/composing-suspending-functions.md b/docs/composing-suspending-functions.md
index dafa8d6..9ee0f0a 100644
--- a/docs/composing-suspending-functions.md
+++ b/docs/composing-suspending-functions.md
@@ -6,8 +6,8 @@
 // This file was automatically generated from coroutines-guide.md by Knit tool. Do not edit.
 package kotlinx.coroutines.guide.$$1$$2
 -->
-<!--- KNIT     ../core/kotlinx-coroutines-core/test/guide/.*\.kt -->
-<!--- TEST_OUT ../core/kotlinx-coroutines-core/test/guide/test/ComposingGuideTest.kt
+<!--- KNIT     ../kotlinx-coroutines-core/jvm/test/guide/.*\.kt -->
+<!--- TEST_OUT ../kotlinx-coroutines-core/jvm/test/guide/test/ComposingGuideTest.kt
 // This file was automatically generated from coroutines-guide.md by Knit tool. Do not edit.
 package kotlinx.coroutines.guide.test
 
@@ -97,7 +97,7 @@
 
 </div>
 
-> You can get full code [here](../core/kotlinx-coroutines-core/test/guide/example-compose-01.kt)
+> You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-compose-01.kt)
 
 It produces something like this:
 
@@ -150,7 +150,7 @@
 
 </div>
 
-> You can get full code [here](../core/kotlinx-coroutines-core/test/guide/example-compose-02.kt)
+> You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-compose-02.kt)
 
 It produces something like this:
 
@@ -204,7 +204,7 @@
 
 </div>
 
-> You can get full code [here](../core/kotlinx-coroutines-core/test/guide/example-compose-03.kt)
+> You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-compose-03.kt)
 
 It produces something like this:
 
@@ -301,7 +301,7 @@
 
 </div>
 
-> You can get full code [here](../core/kotlinx-coroutines-core/test/guide/example-compose-04.kt)
+> You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-compose-04.kt)
 
 <!--- TEST ARBITRARY_TIME
 The answer is 42
@@ -377,7 +377,7 @@
 
 </div>
 
-> You can get full code [here](../core/kotlinx-coroutines-core/test/guide/example-compose-05.kt)
+> You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-compose-05.kt)
 
 We still have concurrent execution of both operations as evident from the output of the above main function: 
 
@@ -424,7 +424,7 @@
 
 </div>
 
-> You can get full code [here](../core/kotlinx-coroutines-core/test/guide/example-compose-06.kt)
+> You can get full code [here](../kotlinx-coroutines-core/jvm/test/guide/example-compose-06.kt)
 
 Note, how both first `async` and awaiting parent are cancelled on the one child failure:
 ```text